Paul Anderson's videos are engaging and clear. You need to chose subject matter that is suitable to your own syllabus, but students can go to particular segments. These lessons are generally 10-15 minutes long and include some excellent graphics. While these are mainly Biology videos there are videos from all sciences and PD videos as well.
Andrew Douch's Biology podcasts are written for VCE, but I have found many useful for HSC. Students enjoy his podcasts and find his jokes endearingly nerdy. "Douchy" provides clear explanations and often helpful hints for memorisation. His more recent podcasts also offer graphics that can be viewed on iPad or iPods. He also has a web site and invites students to email or voicemail and will answer questions. There is also Douchy's Channel which holds his video lessons.
Khan Academy has a huge range of lessons over a large range of subject areas. The format is very straightforward and expository. No exciting graphics, just a disembodied pen (with different colours) and engaging patter from Salman Khan. Again you need to choose your topics carefully and sometimes supplement with instructions as to the level of complexity that is required by your syllabus.
Scootle is a repository for a large number of learning objects. There are activities for all levels and subjects. The learning objects often contain formative quizzes and can be completed without teacher interference.
Sumanas Inc. has a range of interactive animations ~ particularly useful for Biology, but has Astronomy and Chemistry as well. Formative quizzes are also very useful.
Teachers' Domain contains short videos with lesson plans and discussion questions. Often a good source of interesting activities.
Ted Ed has taken some excellent lessons and turned them into video lessons. It also offers quizzes and extension. This section of the TED organisation is relatively new and is expanding almost daily.
YouTube is a fantastic source of videos, as we all know, these are a selection of the more school related/academic videos, so we don't get waylaid by the enormous range on general YouTube
WiHi TV is produced by the Walter & Eliza Hall Institute and show amazing visualisations of biological processes.
Technical Aids
Camtasia (or Jing) from Tech Smith is essential if you wish to make your own lessons. Camtasia films what is on your screen and records your voice. You can make a PowerPoint or Prezi and record your own explanations. You have the option of a 30 day free trial or purchase. You may be able to have your school buy the entire package.
KeepVid allows you to download and save videos from YouTube so that you can ensure that you can always access them, even if you are not connected to the internet.
ShowMe is an app for iPad or other tablets. It enables you to 'write' on your screen (if you have a touch screen). So you can use this to enhance diagrams or other presentations.
Once you've found resources, you can set up your learning platform. I used Moodle.